1. Field of the Invention
This invention relates to generally to medical devices and more particularly to tourniquets, e.g., venous tourniquets which are used during a venipuncture process of withdrawing blood from a limb of a patient, and methods of using the same.
2. Prior Art
The process of venipuncture is eased by the use of a tourniquet to increase tissue pressure to retard venous flow, thereby to facilitate the distention of veins along an extremity such as an arm or leg. By applying a venous tourniquet the vein enlarges, becomes more visible, and the wall is tensioned, helping to facilitate needle entry in the proper location and depth with less prolonged patient discomfort. The tissue pressure achieved is ideally just sufficient to accomplish distension with minimal discomfort, and without interference in arterial flow. Less tissue pressure may be required if the patient is not subject to peripheral venous vasoconstriction, as when the care environment is cool, and venous vasoconstriction influences strive to retain body heat.
A rubber strip is most commonly used as a low cost venous tourniquet, by stretching, then releasing a locked length of strip to apply pressure to the tissue. As the tourniquet is looped and tightened around the extremity, the elastic material narrows and buckles inward as pressure along the arm is focused on less surface area. This property of rubber prevents the tourniquet from realizing the spread profile of pressure which is both effective and comfortable. It is also difficult to estimate the actual pressure being applied when the stretched rubber is released to apply to the extremity. The rubber strip tourniquet is commonly secured with a tuck hitch which may slip and snap back, and uses a variable, uncertain length of strip, further impairing estimation of the actual tissue pressure being applied. Upon securing the tourniquet, the patient often feels a pinching sensation located where the band intersects itself, or due to narrowing of the band with tightening. In addition, the application of the tourniquet typically may move the extremity as the tourniquet is pulled away from the extremity and with over tightening in order to gain enough slack to secure a tuck hitch. Then as the process is finished, the patient may experience additional pinching and hair pull as the skin is stretched along the extremity, and at the tuck. With application of the tourniquet complete, the person applying the tourniquet does not have a direct way of feeling or otherwise appreciating the tension of the tourniquet, no more than necessary to achieve distension. Even experienced users may not consistently provide the appropriate amount of tension. Although under-tension is evident because or poor venous distension, a user may consistently over tension the tourniquet failing to learn to adjust tension appropriately.
Several improvements over the rubber strip have been disclosed in the patent literature. For example, U.S. Pat. No. 3,930,506 (Overand) discloses a disposable tourniquet with an adhesive strip protected by a liner. The feature eliminates the need to tie a tuck hitch, but the release liner has to be removed producing waste material. Moreover, the device is elastic so that it becomes narrower and buckles inward as tension increases. Further still, it has no means to indicate the level of tension.
U.S. Pat. No. 5,219,356 (Harreld) discloses a device which addresses the problem of producing additional waste material by folding over a portion of the tourniquet with the release liner attached. Like the Overand device, the device of Harreld is made with an elastic material and has no tension indication. In addition, the device has no grip for a user's second hand to hold during application, such that the second end of the tourniquet must pass over and rest on top of the fingers (holding the first end in place) before contacting the pressure sensitive adhesive. When the fingers are removed the tension changes unpredictably.
U.S. Published Patent Publication 2007/0250109 (Kerstein et al.) discloses a tourniquet which attempts to solve that problem by introducing a grip region and an aperture or though hole for the other end. However, the feature of Kerstein et al. for achieving that end leads to a several problems. In particular, as the tourniquet is tightened the aperture becomes a pinch point and skin will push though the location. In addition, like the other devices described above the device of Kerstein et al. has no tension indication.
U.S. Pat. No. 5,540,714 (Lundberg et al.) is directed to a disposable tourniquet which prevents slippage making it easier to knot and results in less pulling of skin and hair, but the tourniquet's band still narrows as tension is increased. Moreover, as is the case of the other prior art described above, the device of Lundberg et al. doesn't provide any tension indication.
Several patents do, however, disclose tension indication, e.g., U.S. Pat. No. 3,613,679 (Bijou), U.S. Pat. No. 5,195,950 (Delannoy), U.S. Pat. No. 5,779,659 (Allen) and U.S. Pat. No. 5,894,032 (Green et al.). But these prior art devices all necessitate the use of elastic material as the body of the device in order to function. U.S. Published Patent Application 2009/0062843 (Heston) discloses a device that adds a resilient section to the body of the band. But again elasticity in the body of the device is necessary. U.S. Pat. No 6,149,618 (Sato) provides tension indication by means of a spring which for the purpose of a disposable tourniquet would be cost prohibitive. Comfort features are also described, but the use of the holding ring at the point of intersection between the first and second end of the device would result in skin pushing through the location when tension is applied. A pulley feature is also described, but it lacks a sleeve. Thus, the device cannot slide across the extremity and tissue may be uncomfortably torqued.
U.S. Pat. No. 7,842,067 (Esposito) introduces a sleeve. But there is no direct tension indication other than remembering the number of turns of a rod. Moreover, the features of the Esposito tourniquet constitute a level of complexity which would not be conducive to single use disposable tourniquets.
U.S. Published Patent Application 2008/0177159-A1 (Gavriely) discloses a tourniquet used to stop arterial blood loss that includes a temperature monitor to contribute to diagnostics including to warning signals that usage time is about to expire. There is no provision to indicate ambient temperature to indicate a possible state of peripheral venoconstriction prior to application of a tourniquet to facilitate venipuncture.
To summarize, all of the venous tourniquets described in the prior art suffer from one or more the following disadvantages: pinching of the skin (including where the band intersects itself); pinching and pulling of hair including along the back of the extremity, imprecise or no tension control by the user; use of elastic material which narrows and buckles when stretched, focusing more pressure on less surface; and being cost prohibitive as a disposable tourniquet. Moreover, such devices do not include any ambient temperature feedback to indicate if conditions are ideal for venous distension and typically have excess material which must be removed prior to use or additional behaviors during operation preventing convenient application. Thus, a need presently exists for a low cost, disposable venous tourniquet that enables effective venipuncture with minimal discomfort.
The subject invention addresses that need.